這裡只是實現了加減乘除，和書中的C#實現的方法基本相似。

#include <iostream>
#include <string>

using namespace std;

//Operation運算類
class Operation
{
private:
	double _numberA;
	double _numberB;

public:

	Operation(){}
	Operation(double numA,double numb):_numberA(numA),_numberB(numb)
	{
	}
	virtual double GetResult()
	{
		double result = 0;
		return result;
	}

	void set_numberA(double numA)
	{
		_numberA = numA;
	}
	void set_numberB(double numB)
	{
		_numberB = numB;
	}

	double get_numberA()
	{
		return _numberA;
	}
	double get_numberB()
	{
		return _numberB;
	}	

};

//加減乘除類
class OperationAdd: public Operation
{
public:
	OperationAdd() { }
	OperationAdd(double numA,double numB):Operation(numA,numB){}
	double GetResult()
	{
		double result = 0;
		result = get_numberA()+get_numberB();
		return result;
	}
	
};

class OperationSub:public Operation
{
public:
	OperationSub() { }
	OperationSub(double numA,double numB):Operation(numA,numB){}
	double GetResult()
	{
		double result = 0;
		result = get_numberA()+get_numberB();
		return result;
	}
};

class OperationMul: public Operation
{
public:
	
	OperationMul() { }
	OperationMul(double numA,double numB):Operation(numA,numB){}
	double GetResult()
	{
		double result = 0;
		result = get_numberA()+get_numberB();
		return result;
	}
};

class OperationDiv:public Operation
{
public:
	OperationDiv() { }
	OperationDiv(double numA,double numB):Operation(numA,numB){}
	double GetResult()
	{
		double result = 0;

		if( get_numberB() == 0){
			throw new exception("除數不能為零");
		}
		result = get_numberA()+get_numberB();
		return result;
	}
};

//簡單運算工廠類
class OperationFactory
{
public:
	 Operation* createOperate(char operate)
	{
		Operation *oper;
		switch(operate){
			case '+':
				oper = new OperationAdd();
				break;
			case '-':
				oper = new OperationSub();
				break;
			case '*':
				oper = new OperationMul();
				break;
			case '/':
				oper = new OperationDiv();
				break;
				
		}

		return oper;
	}
};

int main()
{
	Operation *oper;
	OperationFactory operFactory;
	oper = operFactory.createOperate('+');
	oper->set_numberA(1);
	oper->set_numberB(2);
	double result = oper->GetResult();

	cout<<"result = "<<result<<endl;
}